Endocrine System Flashcards

Vocabulary flashcards for the endocrine system lecture.

Homeostasis

The condition of equilibrium or balance in the body’s internal environment due to the interplay of the body’s many regulatory processes.

Gap junctions

Regions between two cells that permit the movement of ions, small solutes or lipid soluble materials from one cell to the other and vice versa.

Paracrine factors

Cellular chemicals released from one cell into the surrounding extracellular fluid that diffuse to the many neighboring cells in the same tissue.

Hormones

Chemicals released by cells directly into the bloodstream that then travel throughout the body to affect target cells.

Target cells

Cells that have receptors to which hormones attach in order to read the hormonal information and react in a certain way.

Endocrine System

Cells and tissues in the body that produce hormones or paracrine factors and release these chemicals directly into the bloodstream.

Amino Acid Derivatives

Small molecules that are structurally related to amino acids, synthesized from tyrosine and tryptophan.

Peptide Hormones

Hormones that are chains of amino acids.

Eicosanoids

Small molecules with a five-carbon ring at one end and derived from arachidonic acid.

Steroid hormones

Lipids derived from cholesterol.

Thyroid and steroid hormones

Hormones that bind to special carrier proteins and remain in circulation much longer.

Catecholamines or peptide hormones

Water-soluble hormones that cannot penetrate the plasma membrane, therefore their receptors are located on the outer surface of the plasma membrane (extracellular receptors).

Eicosanoids

Lipid derivatives that are lipid-soluble and are able to penetrate the plasma membrane to reach receptors on the inner surface of the membrane (intracellular receptors).

Second messenger

An intracellular intermediary needed by a hormone (first messenger) to exert its effects.

G protein

Enzyme complex coupled to a membrane receptor which when activated will bind to GTP to link first and second messengers.

Adenylate cyclase

Enzyme that converts ATP to cyclic-AMP.

Phosphodiesterase (PDE)

Enzyme that inactivates the c-AMP once the desired effect is accomplished.

Phospholipase C (PLC)

Enzyme that causes the production of diacylglycerol (DAG) and inositol triphosphate (IP3) in the plasma membrane.

Protein kinase C (PKC)

Membrane protein which will open up the calcium ion channels allowing extracellular calcium ions to enter the cell.

Calmodulin

Intracellular protein that accelerates the metabolic activity in the cell.

Complex endocrine reflexes

Reflexes that involve one or more intermediary steps and two or more hormones.

Regulatory hormones

Special hormones that control endocrine cells in the adenohypophysis (anterior lobe) of the pituitary gland.

Neuroendocrine reflex

Process where the hypothalamus commands the adrenal medullae to secrete epinephrine and norepinephrine into the bloodstream when the sympathetic division is activated.

Adenohypophysis

The anterior lobe of the pituitary which secretes seven peptide hormones.

Neurohypophysis

The posterior lobe of the pituitary gland which secretes two peptide hormones.

Fenestrated capillaries

Capillaries lined with endothelial cells that are unusually permeable so larger hormones can enter the bloodstream easily.

Thyroid-Stimulating Hormone (TSH)

Hormone that targets the thyroid gland and triggers the release of thyroid hormones (thyroxine, triiodothyronine).

Adrenocorticotropic Hormone (ACTH)

Hormone that stimulates the release of glucocorticoids (steroids that affect glucose metabolism) by the adrenal cortex.

Gonadotropins

Hormones that regulate the activities of the gonads (testes and ovaries).

Follicle-Stimulating Hormone (FSH)

Hormone that promotes follicle development in females and, in combination with LH, stimulates the secretion of estrogens by ovarian cells.

Luteinizing Hormone (LH)

Hormone that induces ovulation (production of ova in females), promotes the secretion of estrogens and progestins by the ovary that prepare the body for possible pregnancy.

Prolactin (PRL)

Hormone that helps stimulate mammary gland development and milk production during and after pregnancy.

Growth Hormone (GH)

Hormone that stimulates cell growth and replication by accelerating the rate of protein synthesis.

Melanocyte Stimulating Hormone (MSH)

Hormone that stimulates the melanocytes of the skin increasing the production of the yellow-brown pigment called melanin.

Antidiuretic Hormone (ADH)

Hormone released in response to a decrease in blood volume or pressure or increase of solute concentration of the blood.

Oxytocin (OXT)

Hormone that stimulates the smooth muscle contractions of the uterus promoting labor and delivery.

Thyroid follicles cells

Hollow spheres lined with simple cuboidal epithelium within the thyroid follicles.

Thyroglobulin

Protein that contains the amino acid tyrosine, which is the building block of thyroid hormones and is deposited into the colloid.

Thyroxine (T4)

Hormone formed when a thyroglobulin molecule contains 4 iodide ions.

Triiodothyronine (T3)

Hormone formed when a thyroglobulin molecule contains 3 iodide ions.

Hypothyroidism (aka myxedema)

Condition that results from the deficiency of T3 and T4.

Hyperthyroidism (thyrotoxicosis)

Condition due to the excess secretion of T3 and T4.

Calcitonin (CT)

Hormone secreted by the C (clear) cells (aka parafollicular cells) which decreases calcium ion concentrations in the body fluids.

Parathyroid hormone (PTH)

Hormone produced by the parathyroid cells which has the opposite function of calcitonin.

Zona Glomerulosa

Outermost region of the adrenal cortex that produces the mineralocorticoids.

Aldosterone

Main mineralocorticoid that stimulates the conservation of sodium ions as well as the elimination of potassium ions at the kidneys, sweat glands, salivary glands, and pancreas.

Zona Fasciculata

Region of the adrenal cortex that produces steroid hormones called glucocorticoids which regulate glucose metabolism.

Cortisol

Main glucocortioid that is secreted in response to ACTH and accelerates the rates of glucose synthesis and glycogen production.

Cushing’s syndrome

Condition due to the release of glucocorticoids in response to excess ACTH secreted by the pituitary gland or excess use of synthetic glucocorticoids.

Zona reticularis

The deepest zone of the adrenal cortex that, under stimulation of ACTH, produces small quantities of androgens.

Adrenal Medulla

The core of the adrenal glands which contain large, round cells innervated by preganglionic sympathetic fibers.

Pinealocytes

Secretory cells within the pineal gland that secrete the hormone melatonin.

Alpha cells

Cells that produce the hormone glucagon in the pancreatic islets.

Beta cell

Cells that produce the hormone insulin in the pancreatic islets.

Insulin

Peptide hormone released into the bloodstream when blood-glucose levels exceed normal levels, when high blood-amino acid levels are too high, or by parasympathetic activation.

Glucagon

Hormone secreted when glucose levels fall below normal that stimulates the breakdown of glycogen stored in skeletal muscle and liver cells.

Type II or non-insulin-dependent diabetes

Type of diabetes where the insulin receptors on the cell membrane become desensitized.

Calcitriol

Hormone that stimulates the absorption of calcium and phosphate ions in the GI tract, the formation and activity of osteoclasts, resorption of calcium ions in the kidneys, and suppresses PTH production.

Erythropoietin

Peptide hormone released in response to low oxygen levels in the kidney tissue which stimulates the production of RBCs in bone marrow.

Renin

Hormone secreted in response to sympathetic stimulation or a decline in renal blood flow.

Natriuretic peptides

Peptides that promote the loss of water and sodium ions at the kidneys and inhibit the secretion of aldosterone and ADH, causing a decrease in blood pressure and volume.

Thymosin

Hormone secreted by the thymus which promotes the development and maturation of lymphocytes.

Testosterone

An androgen that supports the maturation of sperm, protein synthesis in skeletal muscles, male secondary sex characteristics (facial hair, deep voice), and associated behaviors.

Nurse cells

Cells in the testes that secrete inhibin that will target the adenohypophysis in order to inhibit the production of FSH.

Estrogens

Steroid hormones produced by follicular cells in females.

Progestins

Hormones secreted by the corpus luteum that prepares the uterus for implantation, the mammary glands for secretory activity.

Leptin

Peptide hormone released from adipose tissue when we eat which binds to neurons in the hypothalamus resulting in a sense of satiation and the suppression of appetite.